Electric meter.



'No. 698,648. P a tented Apr. 29, I902.

T. DUNCAN.

ELECTRIC METER.

(Application filed. may 24, 1899.)

4 Sheets-Sheet l.. I

(No Model.)

wvmioz Moi 698,648. Patented Apr.'29, 1902.

T. DUNCAN.

ELECTRIC METER.

(Application filed May 24, 1899.) (No Model.) 4 Sheets-Sheet 2.

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No. 698,648. Patented Apr. 29, I902.

T. DUNCAN.

ELECTRIC METER.

(Application filed May 24, 1899.) (No Model.) 4 Sheets-Sheet 3.

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I T. DUNCAN.

ELECTRIC METER.

(Application filed May 24, 1899. (No Model.) 4 Sheets-Sheet 4;

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UNITED STATES PATENT OFFICE.

THOMAS DUNCAN, OF OAKPARK, ILLINOIS, ASSIGNOR TO THE SIEMENS 85 HALSKE ELECTRIC COMPANY OF AMERICA, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

ELECTRIC METER.

SPECIFICATION formingpart of Letters Patent No. 698,648, dated April 29, 1902.

Application filed May 24, 1899. Serial No. 718,023. (No model.)

To all whom it may concern: uring instruments employing such construc- Be it known that I, THOMAS DUNCAN, of tions, since it isnecessary to accuracy that Oakpark, in the county of Cook and State of the current through the instrument shall al- Illinois, have invented certain new and useful ways bear a constant ratio to the current in 5 Improvements in Electric Meters, (Case No. the main circuit which is measured.

51,) of which the following is a specification. A principal object of the invention, there- This invention relates, broadly, to improvefore, is to provide a transformer of such ments in transformers, more particularly of construction that the secondary current will that class which are known in the art as sealways be exactly proportional to the curro ries transformers and which are employed rent through the primary, no matter what the for reducing or transforming heavy to lighter changes in the latter current. alternating currents in a manner analogous Further objects of the invention are to proto the reduction of high-pressure to low-presvide improved construction in meters and sure currents by multiple or parallel transmeasuring instruments employing such imi5 formers. proved transformers and by which currents In its further development the invention of any strength may be measured accurately also relates more specifically to the employ and without difficulty or endangering the inment of the improvements before referred to in struments employed. the production ofimproved electric meters or These objects I am enabled to accomplish z'o measuring instruments for certain classes of by reason of the fact which I have experiwork. The use of series transformersin conmentally discovered that if the secondary of nection with such instruments as a means of a series transformer be connected in shunt measuring the current or energy transmitted around its primarya current may be obtained in circuits in which the current is very heavy through the secondary circuit which will 25 offers many practical advantages, since it is vary in exact accordance with or bear a confound difficult or impossible to construct amstant proportion to the primary or main curmeters, wattmeters, and the like which will rent. This fact is based upon my precedent successfully carry currents above one thoudiscovery that whereas (as is well known and sand amperes. In the electric furnace,'for above stated) the current through the sec-- 0 example, the current used in the'production ondary of an ordinary series transformer inof aluminium, calcium carbid, carborundum, creases more rapidly in proportion than the &c., is frequently so great as to practically current through its primary. The current prohibit the use of instruments which must through a circuit shunted around the pribe connected directly into the circuit, and in mary will increase less rapidly than the pri- 3 5 all such cases it is therefore imperative that mary or main current, so that if two such dea series transformer be employed to reduce rived circuits be combined the tendency of the current to such amount as the meter or the current in the one to increase too rapidly measuring instrument will carry with safety. will be counteracted by the tendency of the Series transformers ashereintofore constructcurrent in the other to increase tooslowly,

0 ed, however, are not well adapted for use in with the resultant effect of a current bearing any situation in which it is necessary that the a constant or straight line ratio to the main 9o currentchanges in the primary and secondary current throughout all variations in the latcircuits should be always accurately'proporter. This being the case, it is only necessary tional to each other, it being well known that to connect the field-coil of the meter or meas- 5 in the present types of such apparatus the uring instrument in such secondary shuntcurrent through the secondary increases at a circuit in order to obtain accurate readings more rapid rate than that through the priof the main circuit.

r mary circuit. This renders it impossible to The invention consists in the matters herein obtain correct results with meters and meats set forth, and more particularly pointed out in the appended claims, and will be fully understood from the following description when read in connection with the accompanying drawings, in which Figure 1 shows a simple arrangement of the primary and secondary circuits in a transformer embodying my invention in one form. Fig. 2 shows the application of my improvements to a wattmeter of the induction-motor type. Fig. 3 shows the improved transformer of Fig. 1 provided with means for adjusting or balancing the circuits to obtain the accurate results desired. Fig. at shows a transformer embodying myimprovementsand conforming more to the type ordinarily employed in practice, the same being used in connection with anintegratingwattmeter, asin Fig. 2. Fig. 5 illustrates an application of the improvements to an indicating-altimeter. Fig. Gilluslustrates their application in connection with an indicating-wattmeter. Fig. 7 shows another style of transformer providedin connection with a wattmeter in accordance with my invention.

In said drawings, A designates the transformer-core, herein shown as made annular or in the form of a ring, but which may be of any desired or suitable shape or construction, and B its primary coil, which is wound upon the core A in the usual manner and connected in series in the main circuit, as shown in Fig. 2. The secondary coil 0 is also wound on the core A in the usual manner, but in accordance with this invention is connected at its terminal 0 to the ends of the primary coil 13, or to the main lead on each side of said primary coil, so that it is shunt around the latter. A field-coil D being then connected in series in this secondary or shunt circuit will be supplied with a current which if the resistance and winding are properly proportiened will vary in exact accordance with the variations in the current through the primary.

The simple elements thus described are shown alone in Fig. 1 and include all essentials of the broad invention, and a transformer so constructed and connected may be advantageously employed in any situation which requires the reduction of a heavy to a light current varying in fixed ratio to the heavy current. The greatest present demand for such apparatus, however, is in connection with meters and measuring instruments, in which the above requirement is essential to accurate results, as hereinbefore stated. In its further development, therefore, the invention contemplates the application of the novel transformer thus described in the construction and installation of such meters and measuring instruments. This merely involves the employment of the coil D as the series fielocoil of the meter, or, in other words, the conneetion of the field-coil of the meter in the secondary shunt-circuit of the transformer. A construction of this kind is shown in Fig. r

2, in which D designates the series field-coil of an integrating wattmeter, F. its shunt or volt coil, and F its revolubly-mounted armature, which is set in rotation by the inductive action of the magnetic fields set up by the coils D and E. G indicates the magnetic drag, H the impedance-coil for lagging the phase of the current of the coil E, and I a secondary shunt-coil provided with an adjustable resistanceiand applied to adjustably modify the action of the impedance-coil II. J designates the generator; L and L, the main leads; M, the transformer for the shunt or volt circuit of the meter, and N the transformer, which supplies any suitable translating devices 0.

Fig. 4 shows a wattmeter installation substantially similar to that just described, except that the transformer core and coils illustrated in this case are of a type more usually employed in practice, the connections and principles of operation being, however, alike in both cases.

Fig. 5 illustrates the invention as applied in connection with an indicating-ammeter l, and Fig. 6 its application in connection with an indicating volt-m eter V,in wh ieh the shun teoil V is mounted to rotate in a familiar manner. An important advantage of the present improvement in all of these applications resides in the possibility of regulating the secondary shunt-current of the transformer to compensate in a large degree for the friction of the parts and to aid in overcoming their inertia in starting. This possibility arises from the resultant nature of the secondary current, it being only necessary to vary the proportions of the windings and resistances in order to vary such current above or below the straight-line ratio. Thus if the secondary coil of the transformer is increased beyond the proportions required for maintaining the resultant eurrentin constant proportion to the main or primary current said resultant current will to this extent have an abnormal rate of in crease, tending to compensate for and overcome the friction and inertia, as above stated. An adjustment with this in view is illustrated in Fig. 8, in which a switch a is provided for the purpose of cutting in or out a greater or less number of convolutions of the secondary coil 0, as may be found necessary, and this or an equivalent device may be provided in connection wit-h any of the meters or instruments referred to, if found desirable.

A very practical transformer construction in accordance with my invention is shown in Fig. 7, in which the main lead is simply run through the center of the annular core A of the transformer, so that it forms, in effect, a primary coil consisting of a single loop. The secondary coil is wound upon the core A, as before, being herein shown as insulated from the lead L by a sleeve or sheath Z, of non-conducting material, and is connected by terminal clamps at c to the lead L on each side of apart, as suggested by the dotted lines at 0 and the resultant secondary current thereby varied to the same end, as by the switch 0 of the construction shown in Fig. 3 and hereinbefore described. The meter connections in this case are the same as those previously set forth. Other translating or current-consuming means may be included in the shunt-conductor with the secondary of the transformer, or this secondary circuit may be used for a variety of purposes, and I do not, therefore,

wish to be limited to the precise disclosure ofthe invention herein set forth, as modifications and adaptations thereof may be made without departing from the spirit of my invention.

I claim as my invention I 1. The combination with a main circuit, of a transformer having its primary coil connected in series in said main circuit and its secondary coil connected in shunt to its primary coil, and an. energizing-coil connected in series in said secondary shunt-circuit.

2. The combination with a series transformer having its secondary connected in shunt to its primary circuit, of a measuring instrument or meter provided with an energizing-coil connected in series in said secondary shunt-circuit.

3. The combination with a main circuit of a transformer having its primary coil connected in series in said main circuit and its secondary coil connected in shunt to its primary coil,.an energizing-coil connected in series in the secondary shunt-circuit, and means for adjustably varying .the relative proportions of the shunt and secondarycoil.

4:. The combination with a main circuit, of a transformer having its primary coil'connected in series in said main circuit and its secondary coil connected in shunt to its primary coil, an energizing-coil connected in series in the secondary shunt-circuit, and means for adjustably varying the length of the secondary coil.

5. The combination with a primary circuit, of means for producing an induced current from the primary current, means for deriving a shunt-current from said primary current, and a meter or measuring instrument energized by the combined action of said induced and shunt currents.

6. In a system of distribution, the combination with a source of alternating current, of a winding receiving current therefrom, a second winding inductively .related to the first and included in a shunt-circuit about the same, and a meter havinga winding includedin the said shunt, substantially as de scribed.

7. In a system of distribution, the combination with a transformer having its primary of few turns and included serially in the circuit, and having its secondary of a larger number of turns and included in a shunt-circuit of said primary,.of a meter having an energizing-winding included in said shunt in series with the secondary, substantially as described.

8. In a system of distribution, the combination with a transformer having its primary of few turns and included serially in the circuit, and having its secondary of a larger number of turns and included in a shunt-circuit of said primary, of a wattmeter having a current field-producing winding included in the shunt-circuit and in series with the secondary, said meter also having a pressure field-winding, substantially as described.

9. In a system of electrical distribution, the combination with a source of alternating current, of a transformer having its primary winding receiving current from the said source, the secondary of the transformer be ing included in a shunt-conductor about the said primary, and a meter having a winding included in the said shunt-conductor, sub stantially as described.

10. The combination with an inducing-coil, of an induced coil in inductive relation there with included in shunt about the said induc ing-coil, and a wattmeterhaving one of its windings included in the said shunt-circuit, substantially as described.

11. The combination with a transformer having its secondary included in a shunt-circuit about its primary, of a wattmeter having a winding includedin the said shunt-circuit, substantially as described.

12. The combination with an inducing-coil, of an induced coil in inductive relation therewith included in shunt about the said inducing-coil, and a wattmeter having its currentwinding included in the said shunt-circuit, substantially as described.

13. The combination with a transformer having its secondary included in a shunt-circuit about its primary, of a wattmeter having its current-winding included in the said shunt-circuit, substantially as described.

In testimony that I claim the foregoing as my inventionIaffiX my signature, in presence of two subscribing witnesses, this 18th day of May, A. D. 1899.

THOMAS DUNCAN.

\Vitnesses:

DAVID F. STAKES, JOHN TODD. 

